1. Field of the Invention
The invention generally relates to a spin valve thin film magnetic element in which electric resistance changes with the relation between the pinned magnetization direction of a pinned magnetic layer and the magnetization direction of a free magnetic layer affected by an external magnetic field, a method of manufacturing the spin valve thin film magnetic element, and a thin film magnetic head comprising the spin valve thin film magnetic element. Particularly, the invention relates to a technique suitable for a spin valve thin film magnetic element capable of decreasing asymmetry and the occurrence of Barkhausen noise, improving the stability of the element, and permitting sufficient control of the magnetic domain of a free magnetic layer.
2. Description of the Related Art
A spin valve thin film element is a GMR (giant magnetoresistive) element exhibiting a giant magnetoresistive effect, and usually is adapted to detect a recording magnetic field from a recording medium such as a hard disk or the like.
As a GMR element, the spin valve thin film magnetic element has a relatively simple structure, excellent properties of a high rate of change in resistance with an external magnetic field, and a change in resistance with a weak magnetic field.
FIG. 29 is a sectional view illustrating the structure of an example of a conventional spin valve thin film element, as viewed from the air bearing surface (ABS) facing a recording medium.
The spin valve thin film magnetic element shown in FIG. 29 is a bottom-type single spin valve thin film element comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer.
In the spin valve thin film element, the moving direction of a magnetic recording medium such as hard disk coincides with the Z direction shown in FIG. 29. The direction of a leakage magnetic field from the magnetic recording medium coincides with the Y direction.
The conventional spin valve thin film element shown in FIG. 29 has a lamination 109 comprising a base layer 106, an antiferromagnetic layer 101, a pinned magnetic layer 102, a nonmagnetic conductive layer 103, a free magnetic layer 104, and a protecting layer 107, which are laminated in turn on a substrate. The conventional spin valve thin film element also has a pair of hard bias layers 105 formed on both sides of the lamination 109 and a pair of electrode layers 108 respectively formed on the hard bias layers 105.
The base layer 106 is made of Ta (tantalum). The antiferromagnetic layer 101 is made of a NiO (nickel oxide) alloy, a FeMn (ferro-manganese) alloy, a NiMn (nickel manganese) alloy, or the like. Each of the pinned magnetic layer 102 and the free magnetic layer 104 is made of Co (colbalt), a NiFe (nickel iron) alloy, or the like. The nonmagnetic conductive layer 103 comprises a Cu (copper) film. Each of the hard bias layers 105 is made of Coxe2x80x94Pt (cobalt-platinum) alloy. Each of the electrode layers 108 is made of Cu or the like.
The pinned magnetic layer 102 is formed in contact with the antiferromagnetic layer 101 to produce an exchange coupling magnetic field (exchange anisotropic magnetic field) in the interface between the pinned magnetic layer 102 and the antiferromagnetic layer 101. The pinned magnetization of the pinned magnetic layer 102 is pinned in the Y direction shown in the drawing.
The hard bias layers 105 are magnetized in the X1 direction shown in the drawing to orient variable magnetization of the free magnetic layer 104 in the X1 direction. As a result, the variable magnetization of the free magnetic layer 104 crosses the pinned magnetization of the pinned magnetic layer 102.
The electrode layers 108 respectively comprise overlay portions 108a, which extend to the portions of the lamination 109 outside the sensing track width Tw. The overlay portions 108a may solve the problem of decreasing reproduced output due to dead regions formed near both edges of the lamination 109.
In the spin valve thin film element, a sensing current is supplied to the pinned magnetic layer 102, the nonmagnetic conductive layer 103, and the free magnetic layer 104 from the electrode layers 108 formed on the hard bias layers 105. The moving direction of the magnetic recording medium such as a hard disk coincides with the Z direction shown in the drawing. When a leakage magnetic field from the magnetic recording medium is applied in the Y direction, magnetization of the free magnetic layer 104 is changed from the X1 direction to the Y direction. The electric resistance value changes with the relation between the change in the magnetization direction of the free magnetic layer 104 and the pinned magnetization direction of the pinned magnetic layer 102. This is referred to as xe2x80x9cmagnetoresistive (MR) effectxe2x80x9d. The leakage magnetic field from the magnetic recording medium is detected by a change in voltage based on the change in the electric resistance value.
The central portion of the lamination 109, except the overlay portions 108a, substantially contributes to reproduction of the recording magnetic field from the magnetic recording medium. The control portion comprises a sensitive region exhibiting the magnetoresistive effect, and defines the sensing track width Tw. The both-side regions below the overlay portions 108a are the dead regions, which substantially do not contribute to reproduction of the recording magnetic field from the magnetic recording medium.
In the spin valve thin film element, the asymmetry of output is desired to be as small as possible and is defined by the relation between the variable magnetization direction of the free magnetic layer 104 and the pinned magnetization direction of the pinned magnetic layer 102. Therefore, the relation between the variable magnetization of the free magnetic layer 104 and the pinned magnetization of the pinned magnetic layer 102 is desired to be as close to 90xc2x0 as possible, and in theory 90xc2x0.
The variable magnetization direction of the free magnetic layer 104 that affects the asymmetry of output is described below based on the drawings.
FIG. 30 is a schematic drawing illustrating a state in which the direction of variable magnetization Mf of the free magnetic layer 104 is defined.
The magnetic fields that influence the direction of variable magnetization Mf of the free magnetic layer 104 include three magnetic fieldsxe2x80x94a sensing current magnetic field Hj due to a sensing current J, a demagnetizing (dipole) magnetic field Hd due to the pinned magnetization of the pinned magnetic layer 102, and an interaction magnetic field Hint due to the layer interaction between the free magnetic layer 104 and the pinned magnetic layer 102.
When these magnetic fields contribute less to the variable magnetization Mf of the free magnetic field 104, asymmetry is decreased. In order to decrease asymmetry, when no external magnetic field is applied, the following condition is satisfied.
Hj+Hd+Hint=0
With the spin valve thin film element not operating, i.e., with no sensing current J supplied, no sensing current magnetic field Hj occurs. In this state, the direction of the variable magnetization Mf of the free magnetic layer 104 is oriented by the magnetic field of the hard bias layers 105. With no sensing current J supplied, the variable magnetization Mf of the free magnetic layer 104 defined by the hard bias layers 105 does not cross perpendicularly to the pinned magnetization Mp of the pinned magnetic layer 102. Therefore, a setting is performed in anticipation of contribution of the sensing current J so that these magnetization directions do not cross each other at right angles unless the sensing current J flows.
With no sensing current J supplied, no sensing current magnetic field Hj is produced and the variable magnetization Mf of the free magnetic field 104 tends to be opposite to the pinned magnetization Mp of the pinned magnetic layer 102.
As shown in FIG. 29, in the spin valve thin film element, the electrode layers 108 formed on the hard bias layers 105 have the overlay portions 108a extending to the top of the lamination 109. As a result, when the sensing current is supplied to the pinned magnetic layer 102, the nonmagnetic conductive layer 103, and the free magnetic layer 104 from the electrode layers 108, the sensing current J mostly flows into the lamination 109 through the overlay portions 108a. 
Therefore, the free magnetic layer 104 comprises a central portion 104a through which the sensing current J flows, and both-side portions (electrode overlay portions) 104b through which little or none of the sensing current J flows.
As described above, in the central portion 104a through which the sensing current J flows, the sensing current magnetic field Hj occurs. The state of Hj+Hd+Hint=0 also occurs, in which contributions of the magnetic fields are balanced. Therefore, with no external magnetic field applied, the variable magnetization Mf of the central portion 104a crosses perpendicularly to the pinned magnetization Mp of the pinned magnetic layer 102.
However, in both-end portions 104b through which essentially no sensing current J flows, as described above, no sensing current magnetic field Hj occurs. The variable magnetization Mf of each of the both-side portions 104b tends to be opposite to the pinned magnetization Mp of the pinned magnetic layer 102. Therefore, with no external magnetic field applied, the variable magnetization Mf of each of the both-side portions 104b does not cross perpendicularly to the pinned magnetization Mp of the pinned magnetic layer 102.
As a result, as shown in FIG. 31, deviations may occur in the magnetization direction of the free magnetic layer 104.
FIG. 31 is a vector map showing the magnetization distribution of the free magnetic layer 104 measured by micro magnetic simulation with a sensing current of 5 mA supplied in a spin valve thin film element without a backed layer.
This drawing shows that the magnetization direction of the central portion 104a of the element is greatly different from the magnetization direction of each of the electrode overlay portions 104b. 
Therefore, in a state in which the free magnetic layer 104 is significantly divided near the edges of the overlay portions 108a as if magnetic walls 104c were formed in the free magnetic layer 104 to interfere with the formation of a single magnetic domain state, as shown in FIG. 32. This may cause nonuniformity in magnetization, and Barkhausen noise or the like which causes instability resulting in incorrect processing of signals from the magnetic recording medium in the spin valve thin film element.
FIG. 33 is a sectional view showing the structure of another example of conventional spin valve thin film elements, as viewed from the air bearing surface (ABS) side facing a recording medium.
Similar to the previously described spin valve thin film element, the spin valve thin film element shown in FIG. 33 is a top-type single spin valve thin film element comprising a ferromagnetic layer, a pinned magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer.
In the spin valve thin film element, the movement direction of the magnetic recording medium such as a hard disk or the like coincides with the Z direction shown in the drawing. The direction of a leakage magnetic field from the magnetic recording medium coincides with the Y direction.
In FIG. 33, reference numeral 121 denotes a base layer provided on a substrate. A free magnetic layer 125 is formed on the base layers 121 and 121a, and a nonmagnetic conductive layer 124 is formed on the free magnetic layer 125. A pinned magnetic layer 123 is formed on the nonmagnetic conductive layer 124. An antiferromagnetic layer 122 is formed on the pinned magnetic layer 123. Furthermore, a protecting layer 127 is formed on the antiferromagnetic layer 122.
Reference numeral 126 denotes a hard bias layer. Reference numeral 128 denotes an electrode layer. Reference numeral 129 denotes a lamination.
In the spin valve thin film magnetic element, the magnetization direction of the pinned magnetic layer 123 is pinned in the direction opposite to the Y direction.
The base layer 121 is made of Ta ,and the antiferromagnetic layer 122 is made of an IrMn (iridium manganese) alloy, an FeMn alloy, a NiMn alloy, or the like. Each of the pinned magnetic layer 123 and the free magnetic layer 125 is made of Co, a NiFe (nickel iron) alloy, or the like. The nonmagnetic conductive layer 124 comprises a Cu film. Each of the hard bias layers 126 is made of a CoPt (cobalt-platinum) alloy. Each of the electrode layers 128 is made of Cu or the like.
The electrode layers 128 formed on the hard bias layers 126 respectively comprise overlay portions 128a which extend to portions of the top of the lamination 129 outside the sensing track width Tw. The overlay portions 128a may solve the problem of decreasing reproduced output due to the dead regions formed near both edges of the lamination 129.
The central portion of the lamination 129 except the overlay portions 128a substantially contributes to reproduction of a recording magnetic field from the magnetic recording medium. The central portion comprises a sensitive region exhibiting the magnetoresistive effect and defining the sensing track width Tw. The both-side regions below the overlay portions 128a are the dead regions that substantially do not contribute to reproduction of the recording magnetic field from the magnetic recording medium.
Like in the example shown in FIG. 29, in the spin valve thin film element, when a sensing current J is supplied to a portion near the pinned magnetic layer 123, the nonmagnetic conductive layer 124, and the free magnetic layer 125 from the electrode layers 128, the sensing current J mostly flows into the lamination 129 through the overlay portions 128a. 
However, in the spin valve thin film element, the antiferromagnetic layer 122 is located in the upper portion of the lamination 129 in contact with the overlay portions 128a. The pinned magnetic layer 123 and the free magnetic layer 125 are present below the antiferromagnetic layer 122. Therefore, in order that the sensing current J flows to the portion near the pinned magnetic layer 123, the nonmagnetic conductive layer 124, and the free magnetic layer 125 through the overlay portions 128a, it is necessary that the sensing current J passes through a portion near the antiferromagnetic layer 122.
The antiferromagnetic layer 122 is made of an IrMn alloy, an FeMn alloy, or a NiMn alloy, which has high resistivity. For example, the IrMn alloy, FeMn alloy, or NiMn (nickel manganese) alloy has a resistivity of about 200 xcexcxcexa9cmxe2x88x921 which is about ten times as high as the resistivity of about 10 xcexcxcexa9cmxe2x88x921 order of a NiFe alloy which constitutes the pinned magnetic layer 123 and the free magnetic layer 125, and which is about hundred times as high as the resistivity of about 1 xcexcxcexa9cmxe2x88x921 order of Cu which constitutes the nonmagnetic conductive layer 124.
Since the antiferromagnetic layer 122 has high resistivity, the sensing current J flowing through the overlay portions 128a shown in FIG. 33 is subjected to high resistance. The component of a shunt Jxe2x80x2 flowing directly into the portion below the antiferromagnetic layer 122 through the hard bias layers 126 becomes so large that it cannot be neglected.
As a result, in FIG. 33, the sensing current flows through regions D of the lamination 129 below the overlay portions 128a. The regions D are the dead regions and cause a change in magnetoresistance thus adding an output signal to the reproduced output of the sensitive region.
Particularly, side reading occurs when the recording track width and the recording track interval are decreased to narrow the track width in a magnetic recording medium with increases in the recording density of the magnetic recording medium. Information on a magnetic recording track adjacent to a magnetic recording track on which information to be read by the sensitive region is read by the regions D, thus causing error due to noise in output signals.
Fundamentally, there is need to improve output characteristics and sensitivity of the spin valve thin film element.
In consideration of the above circumstances, the objects of the invention are as follows:
(1) To improve the output characteristics of a spin valve thin film element;
(2) To decrease asymmetry;
(3) To improve the stability of a reproduced waveform;
(4) To prevent the occurrence of side reading;
(5) To provide a method of manufacturing the above-mentioned spin valve thin film element; and
(6) To provide a thin film magnetic head comprising the spin valve thin film element.
In order to achieve these objects, the invention provides a spin valve thin film element having a substrate, an antiferromagnetic layer, a first pinned magnetic layer, a non-magnetic intermediate layer, a second pinned magnetic layer, a non-magnetic conductive layer, a free magnetic layer, a backed layer, hard bias layers, and electrode layers. The antiferromagnetic layer is formed on the substrate. The first pinned magnetic layer is formed in contact with the antiferromagnetic layer so that the magnetization direction of the first pinned magnetic layer is pinned by an exchange coupling magnetic field with the antiferromagnetic layer The nonmagnetic intermediate layer is formed between the first pinned magnetic layer and a second pinned magnetic layer, in which the magnetization direction of the second pinned magnetic layer is oriented in antiparallel with the magnetization direction of the first pinned magnetic layer. The nonmagnetic conductive layer is formed between the second pinned magnetic layer and the free magnetic layer, in which the magnetization direction of the free magnetic layer is oriented in a direction crossing the magnetization direction of the second pinned magnetic layer. The backed layer has a nonmagnetic conductive material and is formed in contact with the side of the free magnetic layer opposite to the nonmagnetic conductive layer side. Hard bias layers are formed on both sides of a lamination comprising at least the antiferromagnetic layer, the first and second pinned magnetic layers, the nonmagnetic conductive layer, the free magnetic layer, and the backed layer. The hard bias layers orient the magnetization direction of the free magnetic layer in a direction crossing the magnetization direction of the pinned magnetic layers. The electrode layers are formed on the hard bias layers and supply a sensing current to the lamination. The electrode layers are formed to extend from both sides of the lamination to the central portion of the surface of the lamination.
In one aspect, the extension length of one of the electrode layers on both sides of the lamination toward the central portion of the surface of the lamination is set in the range of about 0.1 xcexcm through about 0.5 xcexcm.
In one aspect, the extension length of one of the electrode layers on both sides of the lamination toward the central portion of the surface of the lamination is set in the range of about 0.03 xcexcm through about 0.10 xcexcm.
The lamination may be formed by means for laminating in turn the antiferromagnetic layer, the first pinned magnetic layer, the nonmagnetic intermediate layer, the second pinned layer, the nonmagnetic conductive layer, the free magnetic layer, and the backed layer on the substrate.
In one aspect, the backed layer comprises a material selected from Au (gold), Ag (silver), and Cu.
The protecting layer may be made of Ta and may be formed on the surface of the backed layer.
The intermediate layer may be made of Ta or Cr chromium and may be provided between the backed layer and the hard bias layers.
The intermediate layer may be made of Ta or Cr and may be provided between the backed layer and the electrode layers.
The intermediate layer may be made of Ta or Cr and may be provided between the hard bias layers and the electrode layers.
Each of the electrode layers may comprise a single layer film or a multilayer film and may be made of at least one element selected from Cr, Au, Ta and W (tungsten).
Each of the electrode layers of the present invention may comprise a multilayer film formed by alternately depositing Au and Ta or W.
In one aspect, the hard bias layers are arranged at the same layer position as the free magnetic layer on the substrate. The hard bias layers may be formed so that the upper surfaces thereof are joined to the sides of the lamination at positions nearer the substrate than the upper edges of the sides of the lamination.
In one aspect, the hard bias layers may be formed so that the upper surfaces thereof are joined to the sides of the lamination at positions between the upper and lower surfaces of the free magnetic layer.
In the present invention, the antiferromagnetic layer may comprise any Xxe2x80x94Mn alloy and Ptxe2x80x94Mnxe2x80x94Xxe2x80x2 alloy, where X represents one element selected from Pt, Pd, Ir, Rh, Ru, and Os, and where Xxe2x80x2 represents at least one element selected from Pd, Cr, Ru, Ni, Ir, Rh, Os, Au, Ag, Ne, Ar, Xe, and Kr.
In one aspect, the free magnetic layer may be divided into two layers separated by nonmagnetic intermediate layer so that the divided layers are brought into a ferrimagnetic state in which the magnetization directions are about 180xc2x0 different.
The lamination also may comprise a sensitive region in the central portion that has excellent reproduction sensitivity and substantially exhibits the magnetoresistive effect. The lamination may have dead region which are formed on both sides of the sensitive region, which have poor reproduction sensitivity, and which substantially cannot exhibit the magnetoresistive effect.
The electrode layers formed on both sides of the lamination may be formed to extend to the dead regions of the lamination and adhere to the lamination.
A thin film magnetic head of the present invention may comprise the above-described spin valve thin film magnetic element.
A method of manufacturing a spin valve thin film element according to an embodiment of the invention includes forming a laminated film on a substrate. The laminated film comprises at least an antiferromagnetic layer, a first pinned magnetic layer, a second pinned magnetic layer, a non-magnetic intermediate layer, a free magnetic layer, a non-magnetic conductive layer, and a backed layer. The first pinned magnetic layer is formed in contact with the antiferromagnetic layer so that the magnetization direction is pinned by an exchange coupling magnetic field with the antiferromagnetic layer. The second pinned magnetic layer is formed on the first pinned magnetic layer. The nonmagnetic intermediate layer is provided between the first and second pinned magnetic layers so that the magnetization direction of the second pinned magnetic layer is oriented in antiparallel with the magnetization direction of the first pinned magnetic layer. The free magnetic layer is formed on the second pinned magnetic layer. The nonmagnetic conductive layer is provided between the free magnetic layer and the second pinned magnetic layer so that the magnetization direction of the free magnetic layer is oriented in a direction crossing the magnetization direction of the second pinned magnetic layer. The backed layer is comprised of a nonmagnetic conductive material and is formed in contact with the side of the free magnetic layer opposite to the nonmagnetic conductive layer side. A lift off resist is formed on the laminated film. The lift off resist has notch portions formed on the lower side facing the laminated film. The portions not covered with the lift off resist are removed by ion milling, leaving a portion of the antiferromagnetic layer to form a lamination having a substantially trapezoidal sectional shape. Hard bias layers are formed at the same layer position as the free magnetic layer on both sides of the lamination by any one or a combination of ion beam sputtering, long slow sputtering, collimation sputtering, and the like. The hard bias layers orient the magnetization direction of the free magnetic layer in a direction crossing the magnetization direction of the second pinned magnetic layer. Electrode layers are formed on the hard bias layers and the portions of the lamination, which are opposite to the notch portions of the lift off resist. Any one or a combination of ion beam sputtering, long slow sputtering, collimation sputtering, and the like may be used to form the electrode layers along with a target opposed to the substrate obliquely at an angle with the substrate. The electrode layers supply a sensing current to the lamination.
In one aspect, with respect to the width dimension of the lift off resist in the width direction of the lamination, the width dimension of each of the notch portions in the width direction of the lamination, which do not contact the lamination, may be set in the range of about 0.03 xcexcm through about 0.10 xcexcm.
An alternate method of manufacturing a spin valve thin film element according to an embodiment of the invention includes forming a laminated film on a substrate. The laminated film comprises at least an antiferromagnetic layer, a first pinned magnetic layer, a second pinned magnetic layer, a non-magnetic intermediate layer, a free magnetic layer, a non-magnetic conductive layer, and a backed layer. The first pinned magnetic layer is formed in contact with the antiferromagnetic layer so that the magnetization direction of the first pinned magnetic layer is pinned by an exchange coupling magnetic field with the antiferromagnetic layer. The second pinned magnetic layer is formed on the first pinned magnetic layer. The nonmagnetic intermediate layer is provided between the first and second pinned magnetic layers so that the magnetization direction of the second pinned magnetic layer is oriented in antiparallel with the magnetization direction of the first pinned magnetic layer. The free magnetic layer formed on the second pinned magnetic layer. The nonmagnetic conductive layer is provided between the free magnetic layer and the second pinned magnetic layer so that the magnetization direction free magnetic layer is oriented in a direction crossing the magnetization direction of the second pinned magnetic layer. The backed layer is comprised of a nonmagnetic conductive material and is formed in contact with the side of the free magnetic layer opposite to the nonmagnetic conductive layer side. A first lift off resist is formed on the laminated film. The first lift off resist has notch portions formed on the lower side facing the laminated film. The portions not covered with the first lift off resist are removed by ion milling leaving a portion of the antiferromagnetic layer to form a lamination having a substantially trapezoidal sectional shape. Hard bias layers are formed at the same layer position as the free magnetic layer on both sides of the lamination by any one or a combination of ion beam sputtering, long slow sputtering, collimation sputtering, and the like. The hard bias layers orient the magnetization direction of the free magnetic layer in a direction crossing the magnetization direction of the second pinned magnetic layer. The first lift off resist is separated from the laminated film. A second lift off resist is formed on the laminated film and has a portion in contact with the lamination. The second lift off resist has a smaller width dimension than that of the first lift off resist in the width direction of the lamination, and has notch portions formed on the lower side facing the lamination. Electrode layers are formed on the portions, which are not covered with the second lift off resist, by any one or a combination of ion beam sputtering, long slow sputtering, collimation sputtering, and the like. The electrode layers supply a sensing current to the lamination.
In one aspect, the difference between the width dimensions of the first and second lift off resists in the width direction of the lamination may be set in the range of about 0.2 xcexcm through about 1.0 xcexcm.
In one aspect, with respect to the width dimension of the second lift off resist in the width direction of the lamination, the width dimension of each of the notch portions in the width direction of the lamination, which do not contact the lamination, may be set in the range of about 0.01 xcexcm through about 0.10 xcexcm.
Portions of the surface of the lamination, which are opposite to the notch portions of the lift off resist or the second lift off resist, may be removed by ion milling, reverse sputtering, and the like after the step of forming the hard bias layers.
The antiferromagnetic layer may comprise any one of Xxe2x80x94Mn alloy and Ptxe2x80x94Mnxe2x80x94Xxe2x80x2 alloys, where X represents an element selected from Pt, Pd, Ir, Rh, Ru, and Os, and where Xxe2x80x2 represents at least one element selected from Pd, Cr, Ru, Ni, Ir, Rh, Os, Au, Ag, Ne, Ar, Xe, and Kr.
In one aspect, the sensitive region of the lamination, as measured by a micro track profile technique, is defined as a region in which the output is 50% or more of the maximum reproduced output when a spin valve thin film magnetic element comprises the electrode layers formed on both sides of the lamination. A the spin valve thin film magnetic element is scanned on a microtrack on which a signal has been recorded in the direction of the track width. The dead regions of the lamination are defined as regions on both sides of the sensitive region, in which the output is 50% or less of the maximum output.
In one aspect, the sensitive region of the lamination is formed to have the same dimension as an optical track width dimension (O-Tw).
In a lamination formed by laminating the antiferromagnetic layer, the first pinned magnetic layer, the nonmagnetic intermediate layer, the second pinned magnetic layer, the free magnetic layer, and the backed layer, the whole region of the lamination may not exhibit the magnetoresistive effect. Only the central region may be the sensitive region having excellent reproduction sensitivity, and exhibiting the magnetoresistive effect.
The region of the lamination, which exhibits excellent reproduction sensitivity, may be referred to as the xe2x80x9csensitive regionxe2x80x9d. The regions on both sides of the sensitive region, which exhibit poor reproduction sensitivity, may be referred to as the xe2x80x9cdead regionsxe2x80x9d. The sensitive region and the dead regions of the lamination are measured by the micro track file technique.
The micro track profile technique will be described with reference to FIG. 26.
As shown in FIG. 26, a spin valve thin film magnetic element comprising a lamination exhibiting the magnetoresistive effect, hard bias layers formed on both sides of the lamination, and electrode layers formed on the hard bias layers is formed on a substrate. The electrode layers are formed only on both sides of the lamination, without the overlay portions 108a or 128a shown in FIG. 29 or 33.
Next, the width dimension A of the upper surface of the lamination, which is not coated with the electrode layers, is measured. The width dimension A is defined as the track width Tw (referred to as xe2x80x9coptical track width dimension O-Twxe2x80x9d hereinafter) measured by the optical method.
A predetermined signal is recorded as a micro track on a magnetic recording medium. The spin valve thin film magnetic element is scanned on the micro track in the direction of the track width to measure the relation between the width dimension A of the lamination and reproduced output. Alternatively, the magnetic recording medium on which the micro track has been recorded may be scanned on the spin valve thin film magnetic element in the direction of the track width to measure the relation between the width dimension A of the lamination and reproduced output. The results of measurement are shown in the lower portion of FIG. 26.
The results of measurement indicate that reproduced output is high in a portion near the center of the lamination. Reproduced output is low in portions near both sides of the lamination. The results also indicate that in the portion near the center of the lamination, the magnetoresistive effect is sufficiently exhibited to contribute to the reproducing function. In the portions near both sides, the magnetoresistive effect deteriorates to decrease the reproducing function.
In one aspect, the region of the lamination, which is formed with width dimension B and which produces reproduced output of 50% or more of the maximum reproduced output is defined as the sensitive region. The regions of the lamination, which are formed with width dimension C and which produce reproduced output of 50% or less of the maximum reproduced output are defined as the dead regions.
In one aspect, the nonmagnetic intermediate layer is provided between the first pinned layer and the second pinned layer in the lamination so that the magnetization direction of the second pinned layer is oriented in antiparallel with the magnetization direction of the first pinned magnetic layer. This arrangement forms a synthetic-ferri-pinned type in which the pinned magnetic layers are brought into a ferrimagnetic state. A demagnetizing (dipole) field due to the pinned magnetization of the pinned magnetic layer may be canceled by counteraction between the magnetostatic coupling magnetic fields of the first and second pinned magnetic layers. It is thus possible to decrease the contribution of the demagnetizing (dipole) magnetic field due to the pinned magnetization of the pinned magnetic layer, which affects the variable magnetization direction of the free magnetic layer.
In a spin valve thin film element in which the pinned magnetic layer is divided into two layers with a nonmagnetic intermediate layer provided between the layers, one of the two divided pinned magnetic layers assists in pinning the other pinned magnetic layer in an appropriate direction, thus maintaining the pinned magnetic layer in a very stable state.
In one aspect, no external magnetic field is applied as a contribution to variable magnetization of the free magnetic layer. To decrease asymmetry in one aspect, the sensing current magnetic field Hj due to the sensing current, the demagnetizing (dipole) field Hd due to pinned magnetization of the pinned magnetic layer, and the interaction magnetic field Hint due to the interlayer interaction between the free magnetic layer and the pinned magnetic layer satisfy the following condition.
Hj+Hd+Hint=0
The demagnetizing (dipole) field may be made substantially zero (Hd=0).
The variable magnetization direction of the free magnetic layer may be easily corrected in the desired direction. The variable magnetization direction of the free magnetic layer may be easily controlled to obtain an excellent spin valve thin film element exhibiting low asymmetry.
The asymmetry represents the degree of asymmetry of a reproduced output waveform. A symmetric reproduced output waveform exhibits low asymmetry. The symmetry of the reproduced output waveform is improved as the asymmetry approaches zero.
The asymmetry is zero when the variable magnetization direction of the free magnetic layer crosses perpendicularly to the pinned magnetization direction of the pinned magnetic layer. With a great deviation in asymmetry, information cannot be precisely read from a recording medium and causes error. Therefore, with low asymmetry, the reliability of reproducing signal processing is improved to provide an excellent spin valve thin film element.
In general, the demagnetizing (dipole) field Hd due to pinned magnetization of the single pinned magnetic layer has a nonuniform distribution in which it is high at both ends, and low in the central portion in the direction of the element height. In a portion of the spin valve thin film element, the condition, Hj+Hd+Hint=0, is not completely satisfied, thereby hindering the free magnetic layer from being put into a single magnetic domain state in some cases.
In the pinned magnetic layers having the above-described multilayer structure, the dipole magnetic field Hd may be made substantially zero to prevent the formation of domain walls in the free magnetic layer. This may prevent the occurrence of nonuniform magnetization due to a hindrance to putting the free magnetic layer into a single magnetic domain state, thereby preventing Barkhausen noise or the like which causes instability resulting in incorrectness of processing of signals from the magnetic recording medium in the spin valve thin film element.
In one aspect, the backed layer is made of a nonmagnetic conductive material and is provided in contact with the free magnetic layer. The height of the center of a sensing current flow in the lamination may be changed to the backed layer side, as compared with a state in which with no backed layer provided. The central position is located on the pinned magnetic layer side. This may decrease the intensity of the sensing current magnetic field at the position of the free magnetic layer to decrease the contribution of the sensing current magnetic field to the variable magnetization of the free magnetic layer. The variable magnetization direction of the free magnetic layer may be easily corrected in the desired direction. The variable magnetization direction of the free magnetic layer may be easily controlled for obtaining a spin valve thin film element having small asymmetry.
In one aspect, the backed layer is made of a nonmagnetic conductive material and is provided in contact with the free magnetic layer. The electrode layers are formed to extend from both sides of the lamination to the central portion of the surface of the lamination. The sensing current from flowing from the electrode layers into the junctions between the hard bias layers and the lamination. Therefore, the ratio of the sensing current directly flowing into the lamination without passing through the hard bias layers may be increased. By increasing the contact area between the lamination and the electrode layers, the junction resistance, which does not contribute to the magnetoresistive effect, may be decreased to improve reproduction characteristics.
As described below, the backed layer comprises a material selected from the group consisting of Au, Ag, and Cu. The backed layer may lengthen the mean free path of +spin (up-spin) electrons contributing to the magnetoresistive effect, thereby producing a high rate of change in resistance xcex94R/R due to the spin filter effect in the spin valve thin film element. The backed layer may make the element adaptable to high-density recording.
In one aspect, the lamination is a bottom type comprising the antiferromagnetic layer, the first pinned magnetic layer, the nonmagnetic intermediate layer, the second pinned magnetic layer, the nonmagnetic conductive layer, the free magnetic layer, and the backed layer. These layers are laminated from the bottom, thus increasing the ratio of the sensing current supplied to the lamination without passing through the antiferromagnetic layer having high resistivity. The shunt component of the sensing current may decrease and flows directly into a portion near the first and second pinned magnetic layers, the nonmagnetic conductive layer, and the free magnetic layer, which are located below the antiferromagnetic layer. The shunt component flows through the hard bias layers in a top type. Side reading may be prevented. The spin valve thin film element may be made adaptable to higher density magnetic recording.
In one aspect, the protecting layer is made of Ta and is formed on the surface of the backed layer to protect the lamination from a necessary atmosphere in the manufacturing process.
The intermediate layers may be made of Ta or Cr and are provided between the backed layer and the head bias layers. The intermediate layers function as a diffusion barrier in exposure to high temperature during the subsequent step of curing the insulating resist ultraviolet (UV) curing or hard baking) in the process for manufacturing an inductive head (write head). Thermal diffusion may be prevented between the backed layer made of Cu and the hard bias layers made of a CoPt alloy or the like, preventing deterioration in the magnetic properties of the hard bias layers.
Furthermore, the intermediate layers may be made of Ta or Cr and are provided between the backed layer and the electrode layers. The intermediate layers prevent thermal diffusion between the backed layer and the electrode layers. The backed layers may be made of Cu. The electrode layers may be made of Cr or the like. Thermal diffusion may occur when the backed layer and electrode layers are exposed to high temperature during the curing of the insulating resist (e.g., UV curing or hard baking) in a process for manufacturing an inductive head (e.g., a write head). The intermediate layers prevent deterioration of the film properties in the backed layer and deterioration of the conduction properties in the electrode layers.
The intermediate layers may be made of Ta or Cr and are provided between the hard bias layers and the electrode layers. The intermediate layers prevent thermal diffusion between the electrode layers made of Cr or the like and the hard bias layers made of a CoPt alloy or the like. Thermal diffusion may occur whether hard bias layers and electrode layers are exposed to high temperature during the curing of the insulating resist (e.g., UV curing or hard baking) in the process for manufacturing an inductive head (e.g., write head). The intermediate layers prevent deterioration of the film properties in the hard bias layers.
When Cu is used for the electrode layers, the intermediate layers of Ta function as a diffusion barrier during a thermal process to prevent deterioration in the magnetic properties of the hard bias layers. The thermal process may be curing the resist. When Ta is used for the electrode layers, the intermediate layers of Cr facilitate the deposition of Ta crystals having a low-resistance body-centered cubic structure on Cr.
In one aspect, when each of the electrode layers comprises a single layer film or multilayer film of at least one material selected from Cr, Au, Ta, and W, the resistance value is decreased. When Cr is selected for the electrode layers and is epitaxially grown on Ta to form the electrode layers, the electric resistance value decreases further.
In one aspect, when each of the electrode layers comprises a multilayer film formed by alternately depositing soft Au and hard Ta or W, it is possible to prevent the phenomenon of smearing in that Au of the electrode layers is extended in the subsequent step of polishing, grinding or cutting to cause a electrical short circuit between the electrode layers and a shield or the like.
In one aspect, the hard bias layers are located at the same layer position as the free magnetic layer on the substrate. The upper surfaces of the hard bias layers are joined to the sides of the lamination at positions nearer the substrate than the upper edges of the sides of the lamination. A leakage magnetic field from each of the hard bias layers is less absorbed by a layer located above the lamination. The layer may be an upper shield layer or the like. A decrease in an effective magnetic field applied to the free magnetic layer is prevented. As a result, the free magnetic layer is readily put into a single magnetic domain state. A spin valve thin film element may be obtained with excellent stability in which the domains of the free magnetic layer can be sufficiently controlled.
In the spin valve thin film element, the hard bias layers are arranged at the same layer position as the free magnetic layer. A strong bias magnetic field may be easily applied to the free magnetic layer to put the free magnetic layer in a signal magnetic domain state, thereby decreasing the occurrence of Barkhausen noise.
Furthermore, the upper surfaces of the hard bias layers are joined to the sides of the lamination at positions between the upper and lower surfaces of the free magnetic layer. The magnetization direction of the free magnetic layer may be oriented in the desired direction by magnetization of the hard bias layers. By increasing the contact area between the lamination and the electrodes layers formed on the hard bias layers, the contact resistance to the sensing current in the junction portions between the electrode layers and the lamination may be decreased.
In one aspect, each of the hard bias layers has a thickness greater than the free magnetic layer in the direction of the thickness. At positions away from the lamination, the upper surfaces of the hard bias layers are arranged at positions farther from the substrate than the upper surface of the free magnetic layer.
In this spin valve thin film element, a stronger bias magnetic field may be easily applied to the free magnetic layer to put the free magnetic layer into a single magnetic domain state, further decreasing the occurrence of Barkhausen noise.
A layer xe2x80x9carranged at the same layer position as the free magnetic layerxe2x80x9d includes the state in which at least the hard bias layers and the free magnetic layer are magnetically connected, and includes the state in which the thickness of the junction portions between the hard bias layers and the free magnetic layer is smaller than the thickness of the free magnetic layer.
The upper surfaces of the hard bias layers represent the surfaces opposite to the substrate side.
A xe2x80x9cjunctionxe2x80x9d includes not only a direct connection but also connection to the lamination or the like through a base layer, an intermediate layer, another layer, multiple layers, and the like.
In one aspect of the spin valve thin film element, the antiferromagnetic layer comprises an alloy represented by the formula Xxe2x80x94Mn wherein X represents one element selected from Pt, Pd, Ru, Ir, Rh, and Os, where X is in the range of about 37 atomic % through about 63 atomic %. In another aspect spin valve thin film element, the antiferromagnetic layer comprises an alloy represented by the formula Xxe2x80x2xe2x80x94Ptxe2x80x94Mn, wherein Xxe2x80x2 represents at least one element selected from Pd, Cr, Ru, Ni, Ir, Rh, Os, Au, Ag, Ne, Ar, Xe, and Kr, and wherein the total of Xxe2x80x2+Pt is in the range of about 37 atomic % through about 63 atomic %.
A spin valve thin film element comprising an antiferromagnetic layer made of an alloy represented by the formula Xxe2x80x94Mn or Xxe2x80x2xe2x80x94Ptxe2x80x94Mn exhibits excellent properties such as a high exchange coupling magnetic field, a high blocking temperature, and excellent corrosion resistance, as compared with the use of a NiO alloy, FeMn alloy, or NiMn alloy which is conventionally used for the antiferromagnetic layer.
In one aspect of the spin valve thin film element, a bias base layer made of Cr may be provided between the hard bias layers and the lamination. A bias base layer made of Cr also may be provided between the hard bias layers and the substrate.
By providing a bias base layer comprising Cr with a body-centered cubic crystal structure (bcc structure), the coercive force and remanence ratio of the hard bias layers may be increased. The bias magnetic field necessary for putting the free magnetic layer into a single magnetic domain state also may be increased.
In one aspect of the spin valve thin film element, the free magnetic layer may be divided into two layers. A nonmagnetic intermediate layer may be provided between the layers to create a ferrimagnetic state in which the magnetization directions of the divided layers are about 180xc2x0 different.
In a spin valve thin film element in which the free magnetic layer is divided into two layers with a nonmagnetic intermediate layer provided between the layers, an exchange coupling magnetic field occurs between the two divided free magnetic layers to cause the ferrimagnetic state. The magnetic thickness is decreased to permit sensitive reversal with an external magnetic field.
In one aspect, the lamination comprises the central sensitive region and the dead regions. The central sensitive region exhibits excellent reproduction sensitivity and substantially exhibits the magnetoresistive effect. The dead regions are formed on both sides of the sensitive region and exhibit poor reproduction sensitivity and substantially no magnetoresistive effect. The electrode layers are formed on both sides of the lamination and may be formed to extend to the dead regions of the lamination.
In this case, the sensing current mainly flows through the tips of the electrode layers, which extend to the upper surface of the lamination. If the electrode layers extend into the sensitive region, substantially exhibits the magnetoresistive effect, the sensing current flows less into the portions of the sensitive region that are covered by the electrode layers. The sensitive region sufficiently exhibiting the magnetoresistive effect also produces no reproduced output. Namely, the reproducing track width may be defined by the distance between the electrode layers.
In the spin valve thin film element having a structure shown in FIG. 26, the effective track width is mainly defined by the distance between the right and left hard bias layers. However, the track is narrowed to increase the ratio of the dead regions in the optical track width, thus significantly decreasing the reproduced output of the spin valve thin film element. In a structure in which the track width is defined by the distance between the electrode layers, the dead regions may be located outside the reproducing track to improve reproduced output. Even when the electrode layers cover the sensitive region, no problem occurs.
Furthermore, the objects of the invention may be achieved by the thin film magnetic head comprising the above-mentioned spin valve thin film element.
In a method of manufacturing a spin valve thin film element according to an embodiment of the invention, a resist pattern is formed on a laminated film by forming a lift off resist having notch portions. The lift off resist is followed by etching (e.g. ion milling) to form a lamination. The, hard bias layers and electrode layers are formed in a desired shape by any one or a combination of ion beam sputtering, long slow sputtering, collimation sputtering, and the like. A target is used and is opposed to the substrate in a state where the target is selectively inclined or not inclined at a set inclination angle, thus obtaining the above-mentioned spin valve thin film element.
The width dimension of each of the notch portions may be set to define the length portions of each of the portions of the electrical layers. The width dimension of each of the notch portions, may not contact the lamination. The width direction of the lamination may be relative to the width dimension of the lift off resist in the width direction of the lamination. The dimension in the direction of the track width may be set to define the length dimension of each of the portions of the electrode layers, which are formed inside the notch portions. The overlay portions of the electrode layers may be formed to extend from both sides of the lamination to the central portion of the surface thereof.
The lamination, hard bias layers, and the electrodes may be formed in desired shapes by a one time of formation of a photoresist (lift off resist). The hard bias layers and the electrode layers may be formed in desired shapes by the sputtering process or the like using the target opposed to the substrate in a state in which the target is selectively inclined or not inclined at an angle with the substrate. The spin valve thin film element may be easily obtained through a small number of steps.
In one aspect, the extension length of one of the electrode layers may extend on both sides of the lamination, and may extend to the surface of the lamination toward the other electrode layer. The length of each of the overlay portions may be set in the range of about 0.03 xcexcm through about 0.10 xcexcm by setting the dimension of each of the notch portions in the track width direction. With the overlay portions having a dimension less than about 0.03 xcexcm in the track width direction, the formation of the overlay portions do not exhibit a sufficient effect. When the overlay portions have a dimension over about 0.10 xcexcm in the track width direction, the electrode layers must be deposited by sputtering with a target opposed to the substrate at a high inclination angle. In this case, the electrode layers having a sufficient thickness cannot be formed inside the notch portions. The shunt of the sensing current flowing to the lamination (GMR film) below (substrate side) the thin overlay portions of the electrode layers cannot be neglected, thereby causing a trouble of side reading or the like.
In a method of manufacturing a spin vale thin film element according to an embodiment of the invention, a lamination and hard bias layers are formed using two types of lift off resist having different width dimensions and notch portions formed on a laminated film. Electrode layers are formed in a desired shape by any one or a combination of ion beam sputtering, long slow sputtering, collimation sputtering, and the like. A target is used and is opposed to the substrate in a state above the target is selectively inclined or not inclined at the set inclination angle, thus obtaining the above-mentioned spin valve thin film element.
In the first lift off resist, the width dimension of each of the notch portions in the direction of the track width, i.e., the width dimension of each of the notch portions, which do not contact the lamination, in the width direction of the lamination relative to the width dimension of the lift off resist in the width direction of the lamination. The dimension in the direction of the track width, and the ion beam incidence angle in ion milling may be set to set the dimension of the lamination in the track width direction, and the shape of the hard bias layers.
Similarly, in the second lift off resist, the dimension of the second lift off resist in the direction of the track width may be set to set the length dimension of each of the portions of the electrode layers, i.e., the overlay portions of the electrode layers, which are formed to extend from both sides of the lamination to the central portion of the surface thereof.
In one aspect, the extension length of one of the electrode layers on both sides of the lamination, which extends to the surface of the lamination toward the other electrode layer. The length of each of the overlay portions, may be set in the range of about 0.1 xcexcm through about 0.5 xcexcm by setting the difference between the dimensions of the first and second lift off resists in the direction of the track width. With the overlay portions having a dimension of less than about 0.1 xcexcm in the track width direction, sufficient alignment precision may not be obtained in forming the second lift off resist which may cause difficulties in uniformly forming the right and left overlay portions with high reproducibility, and which may cause variation in off-track characteristics. With the overlay portions having a dimension of over about 0.5 xcexcm in the track width direction, the probability of causing error due to side reading of adjacent tracks is increased.
The dimension of each of the overlay portions in the direction of the track width may be set by setting the difference between the width dimensions of the first and second lift off resists in the width direction (track width direction) of the lamination to be in the range of about 0.2 xcexcm through about 1.0 xcexcm. The difference between the width dimensions of each side portions of the first and second lift off resists may be set in the direction of the track width to be in the range of about 0.1 xcexcm through about 0.5 xcexcm.
In another aspect, portions of the lamination may be removed. The portions are opposed to the notch portions of the lift off resist or the second lift off resist. The portions should be removed by ion milling or reverse sputtering after the hard bias layers are formed. In this case, the protecting layer and the backed layer in the uppermost layer of the lamination may be cleaned by ion milling or reverse sputtering to obtain sufficient connection between the electrode layers and the backed layer, thus decreasing contact resistance. This also permits an intermediate layer of Ta to be provided between the backed layer and the electrode layers. Cr used for the electrode layers may be epitaxially grown on Ta to form the electrode layers, further decreasing the electric resistance value.
While the arrangement of the layers in the spin valve thin film element has been described in several embodiments, the layers may be operatively connected in other fashions as long as the required electrical, mechanical, and magnetic properties of a spin valve are achieved. They may have one or more additional layers between any or all of them.
Other systems, methods, feature and advantages of the invention will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, within the scope of the invention, and protected by the accompanying claims.